The Movistar Yamaha man, bidding to make it three race victories in a row following wins on home soil in Spain and Japan, came off his bike in Friday's second practice session at Phillip Island and ended up sliding down the track on his back.
Lorenzo had earlier set the pace with a hot lap of one minute 29.602 seconds before his fall and he is well aware he was fortunate to walk away unharmed.
"I didn't expect the crash because I was braking more or less at the same point with similar pressure as the previous laps but suddenly, without any warning, the front tyre closed," said the two-time MotoGP world champion.
"Within one tenth of a second I was in the gravel.
"It was quite a violent crash, but luckily it wasn't so hard that I got injured.
"My leathers are completely destroyed, but I am ok, which is the most important thing.
"I think the asymmetrical front tyre was too hard for these cold conditions. These things happen and you just have to learn from it."
Aleix Espargaro (NGM Forward Racing) topped the time sheets in the first run (1:29.749), with Repsol Honda's Marc Marquez third overall combined.
Defending champion Marquez successfully regained his title after finishing second in Japan last weekend to clock up an unassailable lead in the riders' with two races to come after the Australian MotoGP.